Propionibacterium acnes is a relatively slow growing, (typically) obligate anaerobe gram positive bacterium that is linked to the skin condition acne; it can also cause chronic blepharitis and endophthalmitis, the latter particularly following intraocular surgery. The genome of the bacterium has been sequenced and a study of the bacterial genome has shown several genes that can generate enzymes for degrading skin and proteins that may be immunogenic (activate the immune system).

This bacteria is largely commensal and thus present on most people's skin; and lives on fatty acids in the sebaceous glands on sebum secreted by pores. It may also be found throughout the gastrointestinal tract in humans and many other animals. It is named after its ability to generate propionic acid.

When a pore is blocked this anerobic bacteria overgrows and secretes chemicals that break down the wall of the pore, spilling bacteria such as Staphylococcus aureus into the skin, forming an acne lesion (folliculitis).

It has also been found in corneal ulcers, and on very few occasions damaging heart valves leading to endocarditis, and infections of joints (septic arthritis) have been reported.http://encyclopedia.thefreedictionary.com/Propionibacterium+

Propionibacterium species: P. acnes, is a usually harmless microbe that has pathogenic potential. It has beenlinked to certain cases of endocarditis, wound infections, and abscesses. it can infect acne sites on the skin but it doesnot cause them.